The present invention relates to a control method and a control apparatus in a factory automation system (hereafter abbreviated to FA system) including cells formed by a plurality of working machines including at least one automated machine such as a robot.
As for the range indicated by the term "robot" herein, it refers to an automated machine automatically controlled in accordance with a previously taught program to conduct a complicated operation or work. Typically, the "robot" has a multi-axis mechanism. Industrial robots and numerical control machine tools are also comprehended in robots. Furthermore, the "cell" refers to a unit block of a working system for conducting a series of works, and the unit block includes an automated machine such as a robot and peripheral machines (or peripheral devices). Factory automation is typically formed by a combination of a plurality of cells individually having a specific work assigned thereto. A peripheral machine refers to a working machine or device including a conveyor, a parts feeding machine, an end effecter (including a mechanical hand) and so on. The peripheral machine operates in conjunction with an automated machine such as a robot in one cell. The peripheral machine (or device) is simpler in function and generally operated under sequence control.
In a conventional control method of an FA system, a sequencer (programmable controller) for controlling inputs and outputs (hereafter abbreviated to I/O) of various peripheral machines or devices and a robot controller for controlling robots are connected via a parallel I/O. Mainly, the sequencer always monitors signals carried over the I/O of various peripheral machines and the parallel I/O of the robot controller, synchronization of operations of various peripheral machines with operation of robots and exercises sequence control of the entire FA system.
As a known example relating to such a control method of the FA system, a control method of FA system described in JP-A-61-110204 can be mentioned. In this known example, there is described a method for describing programs of the robot controller, a visual device, and the sequencer by using a language having a common unified system.
Typically in the above described conventional technique, robot controllers for controlling respective robots are prepared to control a plurality of robots included in the FA system, and each robot controller is taught a program for making a robot controlled by the robot controller perform one or more works. In this case, each robot must be generally taught a different program. In addition, when robots of different kinds are used, robots must be taught robot programs using robot languages of different systems in many cases.
As for a programming language of the sequencer for performing sequence control over peripheral machines (or devices) other than robots and the entire FA system, a latter diagram is the most popular language at present. However, this is a programming language having a form that is completely different from that of robot languages. Under these circumstances, the person in charge of constructing an FA system must learn several different programming languages. In addition, for controlling one FA system, a plurality of programs must be generated by using these different programming languages. This is one of major factors impeding the improvement in the development efficiency of the control program of the FA system.
As for the control method of FA system described in the aforementioned JP-A-61-110204 (corresponding to U.S. Pat. No. 4,730,258 issued on Mar. 8, 1988), a method of describing programs respectively for the robot controller, visual device, and sequencer by using a common language having one system is described. Thereby, it becomes unnecessary for the user to learn different programming languages. However, the program itself must be divided into and described as individual programs, each for individual processing such as robot control or sequence control so as to conform to the function of the device actually processing the individual program. (In the above described example of the known technique, such a unit program is referred to as task.) The user must produce a plurality of programs (tasks). In the same way as the foregoing, this results in a problem that the development efficiency of the control program of the FA system cannot be improved.
An object of the present invention is to provide a control method, and apparatus, whereby when a unit element (hereafter referred to as cell) including one set of a plurality of working machines is to be constructed to form an FA system, programs for controlling some works including synchronization of operations of the working machines included in the cell are unified as a cell control program, the user can describe directly the work specifications of the cell as a whole without being conscious of the configuration of the control device and without the necessity of producing separate programs by using different programming languages for respective control devices and learning several programming languages, and hence reduction of development man-hour and improvement of development efficiency can be achieved.